1. Technical Field
The present invention relates to a semiconductor device, and more particularly, to a method for manufacturing a semiconductor device which forms a contact plug in predetermined regions of the bit line contact and the storage electrode contact of a highly integrated semiconductor device.
2. Background of the Related Art
The high integration of a semiconductor device requires a micro-pattern forming technique and a micro-pattern processing of a photoresist which is widely used as a mask in an etching process or in an ion-implanting process.
A resolution R of the photoresist film pattern representing a micro degree is proportional to a wavelength (xcex) of light source of a stepper and a process parameter (k), and is inversely proportional to a lens diameter NA (numerical aperture) of a stepper as shown in the following equation.
R=k*xcex/NA, where R=resolution, xcex=wavelength of light source and NA=numerical aperture.xe2x80x83xe2x80x83Equation 1
The wavelength xcex of the light source can be reduced or other process methods can be performed to improve the resolution of the stepper.
First, in order to reduce the Resolution by reducing the wavelength of the stepper so that the process Resolution has limitations of 0.7 xcexcm and 0.5 xcexcm respectively by using a G-line and an I-line steppers having wavelengths of 436 nm and 365 nm respectively, and in order to form micro pattern with a Resolution below 0.5 xcexcm, a stepper is used that has a deep ultra violet light source (DUV) having a short wavelength, for example a KrF laser having a wavelength of 248 nm or an ArF laser having a wavelength of 193 nm.
Also, other methods for reducing the Resolution include: using a phase shift mask instead of a photo mask; employing a contrast enhancement layer (CEL) method in which a separate thin film capable of enhancing an image contrast is formed on an wafer; using a tri layer resist (TLR) method in which an intermediate layer such as Spin-On-Glass (SOG) film is disposed between two photoresist films; and employing a silylation method in which a gas containing silicon is selectively injected on an upper portion of the photoresist films.
Meanwhile, as a semiconductor device becomes highly integrated, the size of a contact hole which connects upper and lower conductor wirings is decreased, the spacing between the contact hole and an adjacent wiring is decreased, and the aspect ratio which is a ratio between a diameter and a depth of the contact hole is increased.
Accordingly, in a highly integrated semiconductor device having multi-layered conductor wirings, in order to form a contact hole, the masks must be aligned precisely one with another during manufacturing processes of the semiconductor device because the process margin is minimized.
In order to maintain a proper spacing between contact holes, any misalignment tolerance when aligning a mask must be minimized, any lens distortion when implementing an exposing process must be minimized, the critical dimension variation when preparing masks and implementing photo lithography processes must be minimized, and the registration between masks must be maximized.
However, it is difficult to form a contact hole in a predetermined region even if a mask is used. Therefore, to overcome this limitation, a self-aligned contact (SAC) technology which forms a contact hole by a self-aligned method is used.
While a polysilicon, a nitride film or an oxidized film can be used can be used as an etching barrier layer in the SAC method, a nitride film is mainly used as an etch barrier.
Although not shown in drawings, a method for manufacturing a conventional semiconductor device using the SAC technology will be explained.
First, a predetermined lower structure, for example, a MOS field effect transistor (MOSFET) having a field oxide and a gate insulating film, and a gate electrode overlapped with a mask oxide film pattern, source/drain regions, etc. are formed on a semiconductor substrate. Then, an etch barrier and an interlayer insulation film made of an oxide film are sequentially formed on an entire surface of the structure.
Subsequently, a photoresist pattern is formed which exposes an interlayer insulation film in a predetermined region of a bit line contact and a storage electrode contact in the semiconductor substrate. The interlayer insulation film exposed by the photoresist pattern is etched by dry etching so as to expose the etch barrier, and a contact hole is formed by etching the etch barrier again.
However, according to the conventional method for manufacturing a semiconductor device, in the case of forming a bit line contact and a storage electrode contact of a device having a design rule of no greater than 0.15 xcexcm, the conventional circle-type contact is problematic in terms of obtaining a contact hole due to misalignment caused by the lithography process. Therefore, it is impossible for such a contact hole to be applied to manufacturing of semiconductor devices.
In order to overcome this, a method is proposed in which an oxide film which is an interlayer insulation film is formed, and the oxide film is etched by using a T-type or I-type contact mask having the same type as an active region, then a conductive layer for a contact plug is then formed and polished using a chemical mechanical polishing (CMP) to form a contact plug.
Although a method for manufacturing the contact plug using the T-type contact mask has enough of a margin for a bit line contact misalignment, it is difficult to obtain a contact region in a device having a design rule of no greater than 0.13 xcexcm due to misalignment in the region where the storage electrode contact is formed and a slope profile generated when the oxide film is etched.
Also, it is very difficult to obtain a high selection ratio for a nitride film using a method for manufacturing the contact plug using the I-type contact mask where the oxide film is etched by shifting a device isolation mask on a device isolation film since the etched area is wider than the mask area.
Generally, the etched area should be smaller than the non-etched area to obtain a high selection ratio for a nitride film when the oxide film is etched. This is because a polymer cannot protect a nitride film when the etched area is larger than the non-etched area.
In addition, the T-type or I-type processes have a problem in that contact resistance and junction leakage current increase because the etching process is performed in an active region of a semiconductor substrate. As a result, the active region of the semiconductor substrate is exposed to a plasma when the oxide film is etched and the region is damaged by the plasma.
Accordingly, a method for manufacturing a semiconductor device is disclosed that substantially overcomes one or more of the above-described problems due to limitations and disadvantages of the related art.
A method for manufacturing a semiconductor device is disclosed which etches a low dielectric material without damaging a semiconductor substrate and which improves the characteristics of contact resistance and current leakage by forming a low dielectric material pattern in the region where a contact plug will be formed by etching a low dielectric material of an isolation film for insulation between contact plugs, by insulating between contact plugs with an insulting interlayer, and by removing the low dielectric material pattern to form a contact plug.
A method for manufacturing a semiconductor device is disclosed which includes the steps of: forming a field oxide layer in a field region of a semiconductor substrate and a MOSFET in an active region of the substrate, wherein a mask insulating film pattern is formed on an upper portion of a gate electrode of the MOSFET and an insulation film spacer is formed on a sidewall of the gate electrode; forming a stack structure of a low dielectric release insulating film pattern which protects a bit line contact and a storage electrode contact and a hard mask layer on the resultant surface; forming an interlayer insulating film in an upper portion of an entire surface and etching the interlayer insulating film and the hard mask layer, thereby exposing the low dielectric release insulating film pattern; removing the exposed low dielectric release insulating film pattern; forming a conductive layer for a contact plug on the entire surface of the resultant; and forming a contact plug by planarization etching process using the mask insulating film pattern as an etch barrier.
A stack structure is formed of a low dielectric release insulating the film pattern and a hard mask layer to protect predetermined regions of the bit line contact and the storage electrode contact in the upper semiconductor substrate where the MOSFET is formed with a T-type or a I-type contact mask, to form an interlayer insulating film which fills a spacing of the stack structure in an upper portion of the entire surface, to planarize, to expose the contact regions by removing the low dielectric release insulating film pattern, and to form a contact plug by forming a conductive layer for a contact plug which fills the exposed contact regions.
Accordingly, a contact plug is formed by obtaining contact regions with a low dielectric release insulating film pattern and filling the regions resulting from removing the low dielectric release insulating film pattern with a conductive layer.
It is to be understood that both the foregoing general description and the following detailed description of the disclosed methods and structures are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.